1. Field of the Invention
The invention relates generally to a tape transport system, and more particularly, to a tape tensioning system which controls the relative rate of rotation of tape take-up and supply reels over a predetermined range of speed ratios, the speed ratios being selected by a servo-control system in response to tape tension.
2. Prior Art
In known web or tape transport systems, there exists a need for improved precision in the control of tape tension at the recording and playback head. Servo-control motors have been used to drive each tape reel in an effort to more precisely control the speed and tension of the tape; while a third motor arrangement is used in a capstan system to drive the tape. Although such three-motor systems have performed well, they are very inefficient in terms of electrical energy utilization. In fact, 90 percent of the overall electrical input energy is wasted as heat. In addition to such inefficiency, motor driven systems are complex, expensive, heavy, and cause thermal problems in certain applications.
In capstan driven systems, negator springs have been used to provide for the differential motion between supply and take-up reels. A good example of a negator spring tension apparatus is described in my previous U.S. Pat. No. 4,145,016 issued on Mar. 20, 1979 and assigned to the assignee hereof. Negator spring transports are useful to help achieve the precise control required with high-density recordings, however, such systems are heavy, and tape tension must be equalized by the use of complicated and expensive magnetic brakes or their equivalents.
The foregoing problems are particularly acute in aircraft and space applications where reliability and weight are important considerations. Moreover, such highly demanding applications require large diameter tape reels to be used with relatively large tape widths to permit substantial data to be accumulated, but only small amounts of electrical power are available.
It is, therefore, an object of this invention to provide a system which precisely controls the tension of a tape or web between a capstan tape drive arrangement and a take-up reel.
It is another object of this invention to provide a tape control system which operates at substantially reduced power consumption levels over conventional reel drive arrangements.
It is a still further object of the invention to provide a light-weight, affordable system which can handle large reels, of the type which can hold up to 12,000 feet of tape at a width of up to 2 inches, such reels being readily exchangeable.
It is yet another object of this invention to provide a tape tension control system wherein the tension is not dependent upon the speed of the tape, and total electrical input power is reduced by eliminating the need for brakes at the reel hubs.